summaryrefslogtreecommitdiffstats
path: root/kernel/net/rds/iw_send.c
blob: 13834780a3089e9e640e470f7b2e8b26c6334b7b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
/*
 * Copyright (c) 2006 Oracle.  All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the
 * OpenIB.org BSD license below:
 *
 *     Redistribution and use in source and binary forms, with or
 *     without modification, are permitted provided that the following
 *     conditions are met:
 *
 *      - Redistributions of source code must retain the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer.
 *
 *      - Redistributions in binary form must reproduce the above
 *        copyright notice, this list of conditions and the following
 *        disclaimer in the documentation and/or other materials
 *        provided with the distribution.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 *
 */
#include <linux/kernel.h>
#include <linux/in.h>
#include <linux/device.h>
#include <linux/dmapool.h>
#include <linux/ratelimit.h>

#include "rds.h"
#include "iw.h"

static void rds_iw_send_rdma_complete(struct rds_message *rm,
				      int wc_status)
{
	int notify_status;

	switch (wc_status) {
	case IB_WC_WR_FLUSH_ERR:
		return;

	case IB_WC_SUCCESS:
		notify_status = RDS_RDMA_SUCCESS;
		break;

	case IB_WC_REM_ACCESS_ERR:
		notify_status = RDS_RDMA_REMOTE_ERROR;
		break;

	default:
		notify_status = RDS_RDMA_OTHER_ERROR;
		break;
	}
	rds_rdma_send_complete(rm, notify_status);
}

static void rds_iw_send_unmap_rdma(struct rds_iw_connection *ic,
				   struct rm_rdma_op *op)
{
	if (op->op_mapped) {
		ib_dma_unmap_sg(ic->i_cm_id->device,
			op->op_sg, op->op_nents,
			op->op_write ? DMA_TO_DEVICE : DMA_FROM_DEVICE);
		op->op_mapped = 0;
	}
}

static void rds_iw_send_unmap_rm(struct rds_iw_connection *ic,
			  struct rds_iw_send_work *send,
			  int wc_status)
{
	struct rds_message *rm = send->s_rm;

	rdsdebug("ic %p send %p rm %p\n", ic, send, rm);

	ib_dma_unmap_sg(ic->i_cm_id->device,
		     rm->data.op_sg, rm->data.op_nents,
		     DMA_TO_DEVICE);

	if (rm->rdma.op_active) {
		rds_iw_send_unmap_rdma(ic, &rm->rdma);

		/* If the user asked for a completion notification on this
		 * message, we can implement three different semantics:
		 *  1.	Notify when we received the ACK on the RDS message
		 *	that was queued with the RDMA. This provides reliable
		 *	notification of RDMA status at the expense of a one-way
		 *	packet delay.
		 *  2.	Notify when the IB stack gives us the completion event for
		 *	the RDMA operation.
		 *  3.	Notify when the IB stack gives us the completion event for
		 *	the accompanying RDS messages.
		 * Here, we implement approach #3. To implement approach #2,
		 * call rds_rdma_send_complete from the cq_handler. To implement #1,
		 * don't call rds_rdma_send_complete at all, and fall back to the notify
		 * handling in the ACK processing code.
		 *
		 * Note: There's no need to explicitly sync any RDMA buffers using
		 * ib_dma_sync_sg_for_cpu - the completion for the RDMA
		 * operation itself unmapped the RDMA buffers, which takes care
		 * of synching.
		 */
		rds_iw_send_rdma_complete(rm, wc_status);

		if (rm->rdma.op_write)
			rds_stats_add(s_send_rdma_bytes, rm->rdma.op_bytes);
		else
			rds_stats_add(s_recv_rdma_bytes, rm->rdma.op_bytes);
	}

	/* If anyone waited for this message to get flushed out, wake
	 * them up now */
	rds_message_unmapped(rm);

	rds_message_put(rm);
	send->s_rm = NULL;
}

void rds_iw_send_init_ring(struct rds_iw_connection *ic)
{
	struct rds_iw_send_work *send;
	u32 i;

	for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
		struct ib_sge *sge;

		send->s_rm = NULL;
		send->s_op = NULL;
		send->s_mapping = NULL;

		send->s_wr.next = NULL;
		send->s_wr.wr_id = i;
		send->s_wr.sg_list = send->s_sge;
		send->s_wr.num_sge = 1;
		send->s_wr.opcode = IB_WR_SEND;
		send->s_wr.send_flags = 0;
		send->s_wr.ex.imm_data = 0;

		sge = rds_iw_data_sge(ic, send->s_sge);
		sge->lkey = 0;

		sge = rds_iw_header_sge(ic, send->s_sge);
		sge->addr = ic->i_send_hdrs_dma + (i * sizeof(struct rds_header));
		sge->length = sizeof(struct rds_header);
		sge->lkey = 0;

		send->s_mr = ib_alloc_fast_reg_mr(ic->i_pd, fastreg_message_size);
		if (IS_ERR(send->s_mr)) {
			printk(KERN_WARNING "RDS/IW: ib_alloc_fast_reg_mr failed\n");
			break;
		}

		send->s_page_list = ib_alloc_fast_reg_page_list(
			ic->i_cm_id->device, fastreg_message_size);
		if (IS_ERR(send->s_page_list)) {
			printk(KERN_WARNING "RDS/IW: ib_alloc_fast_reg_page_list failed\n");
			break;
		}
	}
}

void rds_iw_send_clear_ring(struct rds_iw_connection *ic)
{
	struct rds_iw_send_work *send;
	u32 i;

	for (i = 0, send = ic->i_sends; i < ic->i_send_ring.w_nr; i++, send++) {
		BUG_ON(!send->s_mr);
		ib_dereg_mr(send->s_mr);
		BUG_ON(!send->s_page_list);
		ib_free_fast_reg_page_list(send->s_page_list);
		if (send->s_wr.opcode == 0xdead)
			continue;
		if (send->s_rm)
			rds_iw_send_unmap_rm(ic, send, IB_WC_WR_FLUSH_ERR);
		if (send->s_op)
			rds_iw_send_unmap_rdma(ic, send->s_op);
	}
}

/*
 * The _oldest/_free ring operations here race cleanly with the alloc/unalloc
 * operations performed in the send path.  As the sender allocs and potentially
 * unallocs the next free entry in the ring it doesn't alter which is
 * the next to be freed, which is what this is concerned with.
 */
void rds_iw_send_cq_comp_handler(struct ib_cq *cq, void *context)
{
	struct rds_connection *conn = context;
	struct rds_iw_connection *ic = conn->c_transport_data;
	struct ib_wc wc;
	struct rds_iw_send_work *send;
	u32 completed;
	u32 oldest;
	u32 i;
	int ret;

	rdsdebug("cq %p conn %p\n", cq, conn);
	rds_iw_stats_inc(s_iw_tx_cq_call);
	ret = ib_req_notify_cq(cq, IB_CQ_NEXT_COMP);
	if (ret)
		rdsdebug("ib_req_notify_cq send failed: %d\n", ret);

	while (ib_poll_cq(cq, 1, &wc) > 0) {
		rdsdebug("wc wr_id 0x%llx status %u byte_len %u imm_data %u\n",
			 (unsigned long long)wc.wr_id, wc.status, wc.byte_len,
			 be32_to_cpu(wc.ex.imm_data));
		rds_iw_stats_inc(s_iw_tx_cq_event);

		if (wc.status != IB_WC_SUCCESS) {
			printk(KERN_ERR "WC Error:  status = %d opcode = %d\n", wc.status, wc.opcode);
			break;
		}

		if (wc.opcode == IB_WC_LOCAL_INV && wc.wr_id == RDS_IW_LOCAL_INV_WR_ID) {
			ic->i_fastreg_posted = 0;
			continue;
		}

		if (wc.opcode == IB_WC_FAST_REG_MR && wc.wr_id == RDS_IW_FAST_REG_WR_ID) {
			ic->i_fastreg_posted = 1;
			continue;
		}

		if (wc.wr_id == RDS_IW_ACK_WR_ID) {
			if (time_after(jiffies, ic->i_ack_queued + HZ/2))
				rds_iw_stats_inc(s_iw_tx_stalled);
			rds_iw_ack_send_complete(ic);
			continue;
		}

		oldest = rds_iw_ring_oldest(&ic->i_send_ring);

		completed = rds_iw_ring_completed(&ic->i_send_ring, wc.wr_id, oldest);

		for (i = 0; i < completed; i++) {
			send = &ic->i_sends[oldest];

			/* In the error case, wc.opcode sometimes contains garbage */
			switch (send->s_wr.opcode) {
			case IB_WR_SEND:
				if (send->s_rm)
					rds_iw_send_unmap_rm(ic, send, wc.status);
				break;
			case IB_WR_FAST_REG_MR:
			case IB_WR_RDMA_WRITE:
			case IB_WR_RDMA_READ:
			case IB_WR_RDMA_READ_WITH_INV:
				/* Nothing to be done - the SG list will be unmapped
				 * when the SEND completes. */
				break;
			default:
				printk_ratelimited(KERN_NOTICE
						"RDS/IW: %s: unexpected opcode 0x%x in WR!\n",
						__func__, send->s_wr.opcode);
				break;
			}

			send->s_wr.opcode = 0xdead;
			send->s_wr.num_sge = 1;
			if (time_after(jiffies, send->s_queued + HZ/2))
				rds_iw_stats_inc(s_iw_tx_stalled);

			/* If a RDMA operation produced an error, signal this right
			 * away. If we don't, the subsequent SEND that goes with this
			 * RDMA will be canceled with ERR_WFLUSH, and the application
			 * never learn that the RDMA failed. */
			if (unlikely(wc.status == IB_WC_REM_ACCESS_ERR && send->s_op)) {
				struct rds_message *rm;

				rm = rds_send_get_message(conn, send->s_op);
				if (rm)
					rds_iw_send_rdma_complete(rm, wc.status);
			}

			oldest = (oldest + 1) % ic->i_send_ring.w_nr;
		}

		rds_iw_ring_free(&ic->i_send_ring, completed);

		if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags) ||
		    test_bit(0, &conn->c_map_queued))
			queue_delayed_work(rds_wq, &conn->c_send_w, 0);

		/* We expect errors as the qp is drained during shutdown */
		if (wc.status != IB_WC_SUCCESS && rds_conn_up(conn)) {
			rds_iw_conn_error(conn,
				"send completion on %pI4 "
				"had status %u, disconnecting and reconnecting\n",
				&conn->c_faddr, wc.status);
		}
	}
}

/*
 * This is the main function for allocating credits when sending
 * messages.
 *
 * Conceptually, we have two counters:
 *  -	send credits: this tells us how many WRs we're allowed
 *	to submit without overruning the receiver's queue. For
 *	each SEND WR we post, we decrement this by one.
 *
 *  -	posted credits: this tells us how many WRs we recently
 *	posted to the receive queue. This value is transferred
 *	to the peer as a "credit update" in a RDS header field.
 *	Every time we transmit credits to the peer, we subtract
 *	the amount of transferred credits from this counter.
 *
 * It is essential that we avoid situations where both sides have
 * exhausted their send credits, and are unable to send new credits
 * to the peer. We achieve this by requiring that we send at least
 * one credit update to the peer before exhausting our credits.
 * When new credits arrive, we subtract one credit that is withheld
 * until we've posted new buffers and are ready to transmit these
 * credits (see rds_iw_send_add_credits below).
 *
 * The RDS send code is essentially single-threaded; rds_send_xmit
 * grabs c_send_lock to ensure exclusive access to the send ring.
 * However, the ACK sending code is independent and can race with
 * message SENDs.
 *
 * In the send path, we need to update the counters for send credits
 * and the counter of posted buffers atomically - when we use the
 * last available credit, we cannot allow another thread to race us
 * and grab the posted credits counter.  Hence, we have to use a
 * spinlock to protect the credit counter, or use atomics.
 *
 * Spinlocks shared between the send and the receive path are bad,
 * because they create unnecessary delays. An early implementation
 * using a spinlock showed a 5% degradation in throughput at some
 * loads.
 *
 * This implementation avoids spinlocks completely, putting both
 * counters into a single atomic, and updating that atomic using
 * atomic_add (in the receive path, when receiving fresh credits),
 * and using atomic_cmpxchg when updating the two counters.
 */
int rds_iw_send_grab_credits(struct rds_iw_connection *ic,
			     u32 wanted, u32 *adv_credits, int need_posted, int max_posted)
{
	unsigned int avail, posted, got = 0, advertise;
	long oldval, newval;

	*adv_credits = 0;
	if (!ic->i_flowctl)
		return wanted;

try_again:
	advertise = 0;
	oldval = newval = atomic_read(&ic->i_credits);
	posted = IB_GET_POST_CREDITS(oldval);
	avail = IB_GET_SEND_CREDITS(oldval);

	rdsdebug("wanted=%u credits=%u posted=%u\n",
			wanted, avail, posted);

	/* The last credit must be used to send a credit update. */
	if (avail && !posted)
		avail--;

	if (avail < wanted) {
		struct rds_connection *conn = ic->i_cm_id->context;

		/* Oops, there aren't that many credits left! */
		set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
		got = avail;
	} else {
		/* Sometimes you get what you want, lalala. */
		got = wanted;
	}
	newval -= IB_SET_SEND_CREDITS(got);

	/*
	 * If need_posted is non-zero, then the caller wants
	 * the posted regardless of whether any send credits are
	 * available.
	 */
	if (posted && (got || need_posted)) {
		advertise = min_t(unsigned int, posted, max_posted);
		newval -= IB_SET_POST_CREDITS(advertise);
	}

	/* Finally bill everything */
	if (atomic_cmpxchg(&ic->i_credits, oldval, newval) != oldval)
		goto try_again;

	*adv_credits = advertise;
	return got;
}

void rds_iw_send_add_credits(struct rds_connection *conn, unsigned int credits)
{
	struct rds_iw_connection *ic = conn->c_transport_data;

	if (credits == 0)
		return;

	rdsdebug("credits=%u current=%u%s\n",
			credits,
			IB_GET_SEND_CREDITS(atomic_read(&ic->i_credits)),
			test_bit(RDS_LL_SEND_FULL, &conn->c_flags) ? ", ll_send_full" : "");

	atomic_add(IB_SET_SEND_CREDITS(credits), &ic->i_credits);
	if (test_and_clear_bit(RDS_LL_SEND_FULL, &conn->c_flags))
		queue_delayed_work(rds_wq, &conn->c_send_w, 0);

	WARN_ON(IB_GET_SEND_CREDITS(credits) >= 16384);

	rds_iw_stats_inc(s_iw_rx_credit_updates);
}

void rds_iw_advertise_credits(struct rds_connection *conn, unsigned int posted)
{
	struct rds_iw_connection *ic = conn->c_transport_data;

	if (posted == 0)
		return;

	atomic_add(IB_SET_POST_CREDITS(posted), &ic->i_credits);

	/* Decide whether to send an update to the peer now.
	 * If we would send a credit update for every single buffer we
	 * post, we would end up with an ACK storm (ACK arrives,
	 * consumes buffer, we refill the ring, send ACK to remote
	 * advertising the newly posted buffer... ad inf)
	 *
	 * Performance pretty much depends on how often we send
	 * credit updates - too frequent updates mean lots of ACKs.
	 * Too infrequent updates, and the peer will run out of
	 * credits and has to throttle.
	 * For the time being, 16 seems to be a good compromise.
	 */
	if (IB_GET_POST_CREDITS(atomic_read(&ic->i_credits)) >= 16)
		set_bit(IB_ACK_REQUESTED, &ic->i_ack_flags);
}

static inline void
rds_iw_xmit_populate_wr(struct rds_iw_connection *ic,
		struct rds_iw_send_work *send, unsigned int pos,
		unsigned long buffer, unsigned int length,
		int send_flags)
{
	struct ib_sge *sge;

	WARN_ON(pos != send - ic->i_sends);

	send->s_wr.send_flags = send_flags;
	send->s_wr.opcode = IB_WR_SEND;
	send->s_wr.num_sge = 2;
	send->s_wr.next = NULL;
	send->s_queued = jiffies;
	send->s_op = NULL;

	if (length != 0) {
		sge = rds_iw_data_sge(ic, send->s_sge);
		sge->addr = buffer;
		sge->length = length;
		sge->lkey = rds_iw_local_dma_lkey(ic);

		sge = rds_iw_header_sge(ic, send->s_sge);
	} else {
		/* We're sending a packet with no payload. There is only
		 * one SGE */
		send->s_wr.num_sge = 1;
		sge = &send->s_sge[0];
	}

	sge->addr = ic->i_send_hdrs_dma + (pos * sizeof(struct rds_header));
	sge->length = sizeof(struct rds_header);
	sge->lkey = rds_iw_local_dma_lkey(ic);
}

/*
 * This can be called multiple times for a given message.  The first time
 * we see a message we map its scatterlist into the IB device so that
 * we can provide that mapped address to the IB scatter gather entries
 * in the IB work requests.  We translate the scatterlist into a series
 * of work requests that fragment the message.  These work requests complete
 * in order so we pass ownership of the message to the completion handler
 * once we send the final fragment.
 *
 * The RDS core uses the c_send_lock to only enter this function once
 * per connection.  This makes sure that the tx ring alloc/unalloc pairs
 * don't get out of sync and confuse the ring.
 */
int rds_iw_xmit(struct rds_connection *conn, struct rds_message *rm,
		unsigned int hdr_off, unsigned int sg, unsigned int off)
{
	struct rds_iw_connection *ic = conn->c_transport_data;
	struct ib_device *dev = ic->i_cm_id->device;
	struct rds_iw_send_work *send = NULL;
	struct rds_iw_send_work *first;
	struct rds_iw_send_work *prev;
	struct ib_send_wr *failed_wr;
	struct scatterlist *scat;
	u32 pos;
	u32 i;
	u32 work_alloc;
	u32 credit_alloc;
	u32 posted;
	u32 adv_credits = 0;
	int send_flags = 0;
	int sent;
	int ret;
	int flow_controlled = 0;

	BUG_ON(off % RDS_FRAG_SIZE);
	BUG_ON(hdr_off != 0 && hdr_off != sizeof(struct rds_header));

	/* Fastreg support */
	if (rds_rdma_cookie_key(rm->m_rdma_cookie) && !ic->i_fastreg_posted) {
		ret = -EAGAIN;
		goto out;
	}

	/* FIXME we may overallocate here */
	if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0)
		i = 1;
	else
		i = ceil(be32_to_cpu(rm->m_inc.i_hdr.h_len), RDS_FRAG_SIZE);

	work_alloc = rds_iw_ring_alloc(&ic->i_send_ring, i, &pos);
	if (work_alloc == 0) {
		set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
		rds_iw_stats_inc(s_iw_tx_ring_full);
		ret = -ENOMEM;
		goto out;
	}

	credit_alloc = work_alloc;
	if (ic->i_flowctl) {
		credit_alloc = rds_iw_send_grab_credits(ic, work_alloc, &posted, 0, RDS_MAX_ADV_CREDIT);
		adv_credits += posted;
		if (credit_alloc < work_alloc) {
			rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc - credit_alloc);
			work_alloc = credit_alloc;
			flow_controlled++;
		}
		if (work_alloc == 0) {
			set_bit(RDS_LL_SEND_FULL, &conn->c_flags);
			rds_iw_stats_inc(s_iw_tx_throttle);
			ret = -ENOMEM;
			goto out;
		}
	}

	/* map the message the first time we see it */
	if (!ic->i_rm) {
		/*
		printk(KERN_NOTICE "rds_iw_xmit prep msg dport=%u flags=0x%x len=%d\n",
				be16_to_cpu(rm->m_inc.i_hdr.h_dport),
				rm->m_inc.i_hdr.h_flags,
				be32_to_cpu(rm->m_inc.i_hdr.h_len));
		   */
		if (rm->data.op_nents) {
			rm->data.op_count = ib_dma_map_sg(dev,
							  rm->data.op_sg,
							  rm->data.op_nents,
							  DMA_TO_DEVICE);
			rdsdebug("ic %p mapping rm %p: %d\n", ic, rm, rm->data.op_count);
			if (rm->data.op_count == 0) {
				rds_iw_stats_inc(s_iw_tx_sg_mapping_failure);
				rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc);
				ret = -ENOMEM; /* XXX ? */
				goto out;
			}
		} else {
			rm->data.op_count = 0;
		}

		ic->i_unsignaled_wrs = rds_iw_sysctl_max_unsig_wrs;
		ic->i_unsignaled_bytes = rds_iw_sysctl_max_unsig_bytes;
		rds_message_addref(rm);
		ic->i_rm = rm;

		/* Finalize the header */
		if (test_bit(RDS_MSG_ACK_REQUIRED, &rm->m_flags))
			rm->m_inc.i_hdr.h_flags |= RDS_FLAG_ACK_REQUIRED;
		if (test_bit(RDS_MSG_RETRANSMITTED, &rm->m_flags))
			rm->m_inc.i_hdr.h_flags |= RDS_FLAG_RETRANSMITTED;

		/* If it has a RDMA op, tell the peer we did it. This is
		 * used by the peer to release use-once RDMA MRs. */
		if (rm->rdma.op_active) {
			struct rds_ext_header_rdma ext_hdr;

			ext_hdr.h_rdma_rkey = cpu_to_be32(rm->rdma.op_rkey);
			rds_message_add_extension(&rm->m_inc.i_hdr,
					RDS_EXTHDR_RDMA, &ext_hdr, sizeof(ext_hdr));
		}
		if (rm->m_rdma_cookie) {
			rds_message_add_rdma_dest_extension(&rm->m_inc.i_hdr,
					rds_rdma_cookie_key(rm->m_rdma_cookie),
					rds_rdma_cookie_offset(rm->m_rdma_cookie));
		}

		/* Note - rds_iw_piggyb_ack clears the ACK_REQUIRED bit, so
		 * we should not do this unless we have a chance of at least
		 * sticking the header into the send ring. Which is why we
		 * should call rds_iw_ring_alloc first. */
		rm->m_inc.i_hdr.h_ack = cpu_to_be64(rds_iw_piggyb_ack(ic));
		rds_message_make_checksum(&rm->m_inc.i_hdr);

		/*
		 * Update adv_credits since we reset the ACK_REQUIRED bit.
		 */
		rds_iw_send_grab_credits(ic, 0, &posted, 1, RDS_MAX_ADV_CREDIT - adv_credits);
		adv_credits += posted;
		BUG_ON(adv_credits > 255);
	}

	send = &ic->i_sends[pos];
	first = send;
	prev = NULL;
	scat = &rm->data.op_sg[sg];
	sent = 0;
	i = 0;

	/* Sometimes you want to put a fence between an RDMA
	 * READ and the following SEND.
	 * We could either do this all the time
	 * or when requested by the user. Right now, we let
	 * the application choose.
	 */
	if (rm->rdma.op_active && rm->rdma.op_fence)
		send_flags = IB_SEND_FENCE;

	/*
	 * We could be copying the header into the unused tail of the page.
	 * That would need to be changed in the future when those pages might
	 * be mapped userspace pages or page cache pages.  So instead we always
	 * use a second sge and our long-lived ring of mapped headers.  We send
	 * the header after the data so that the data payload can be aligned on
	 * the receiver.
	 */

	/* handle a 0-len message */
	if (be32_to_cpu(rm->m_inc.i_hdr.h_len) == 0) {
		rds_iw_xmit_populate_wr(ic, send, pos, 0, 0, send_flags);
		goto add_header;
	}

	/* if there's data reference it with a chain of work reqs */
	for (; i < work_alloc && scat != &rm->data.op_sg[rm->data.op_count]; i++) {
		unsigned int len;

		send = &ic->i_sends[pos];

		len = min(RDS_FRAG_SIZE, ib_sg_dma_len(dev, scat) - off);
		rds_iw_xmit_populate_wr(ic, send, pos,
				ib_sg_dma_address(dev, scat) + off, len,
				send_flags);

		/*
		 * We want to delay signaling completions just enough to get
		 * the batching benefits but not so much that we create dead time
		 * on the wire.
		 */
		if (ic->i_unsignaled_wrs-- == 0) {
			ic->i_unsignaled_wrs = rds_iw_sysctl_max_unsig_wrs;
			send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
		}

		ic->i_unsignaled_bytes -= len;
		if (ic->i_unsignaled_bytes <= 0) {
			ic->i_unsignaled_bytes = rds_iw_sysctl_max_unsig_bytes;
			send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
		}

		/*
		 * Always signal the last one if we're stopping due to flow control.
		 */
		if (flow_controlled && i == (work_alloc-1))
			send->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;

		rdsdebug("send %p wr %p num_sge %u next %p\n", send,
			 &send->s_wr, send->s_wr.num_sge, send->s_wr.next);

		sent += len;
		off += len;
		if (off == ib_sg_dma_len(dev, scat)) {
			scat++;
			off = 0;
		}

add_header:
		/* Tack on the header after the data. The header SGE should already
		 * have been set up to point to the right header buffer. */
		memcpy(&ic->i_send_hdrs[pos], &rm->m_inc.i_hdr, sizeof(struct rds_header));

		if (0) {
			struct rds_header *hdr = &ic->i_send_hdrs[pos];

			printk(KERN_NOTICE "send WR dport=%u flags=0x%x len=%d\n",
				be16_to_cpu(hdr->h_dport),
				hdr->h_flags,
				be32_to_cpu(hdr->h_len));
		}
		if (adv_credits) {
			struct rds_header *hdr = &ic->i_send_hdrs[pos];

			/* add credit and redo the header checksum */
			hdr->h_credit = adv_credits;
			rds_message_make_checksum(hdr);
			adv_credits = 0;
			rds_iw_stats_inc(s_iw_tx_credit_updates);
		}

		if (prev)
			prev->s_wr.next = &send->s_wr;
		prev = send;

		pos = (pos + 1) % ic->i_send_ring.w_nr;
	}

	/* Account the RDS header in the number of bytes we sent, but just once.
	 * The caller has no concept of fragmentation. */
	if (hdr_off == 0)
		sent += sizeof(struct rds_header);

	/* if we finished the message then send completion owns it */
	if (scat == &rm->data.op_sg[rm->data.op_count]) {
		prev->s_rm = ic->i_rm;
		prev->s_wr.send_flags |= IB_SEND_SIGNALED | IB_SEND_SOLICITED;
		ic->i_rm = NULL;
	}

	if (i < work_alloc) {
		rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc - i);
		work_alloc = i;
	}
	if (ic->i_flowctl && i < credit_alloc)
		rds_iw_send_add_credits(conn, credit_alloc - i);

	/* XXX need to worry about failed_wr and partial sends. */
	failed_wr = &first->s_wr;
	ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
	rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
		 first, &first->s_wr, ret, failed_wr);
	BUG_ON(failed_wr != &first->s_wr);
	if (ret) {
		printk(KERN_WARNING "RDS/IW: ib_post_send to %pI4 "
		       "returned %d\n", &conn->c_faddr, ret);
		rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc);
		if (prev->s_rm) {
			ic->i_rm = prev->s_rm;
			prev->s_rm = NULL;
		}
		goto out;
	}

	ret = sent;
out:
	BUG_ON(adv_credits);
	return ret;
}

static void rds_iw_build_send_fastreg(struct rds_iw_device *rds_iwdev, struct rds_iw_connection *ic, struct rds_iw_send_work *send, int nent, int len, u64 sg_addr)
{
	BUG_ON(nent > send->s_page_list->max_page_list_len);
	/*
	 * Perform a WR for the fast_reg_mr. Each individual page
	 * in the sg list is added to the fast reg page list and placed
	 * inside the fast_reg_mr WR.
	 */
	send->s_wr.opcode = IB_WR_FAST_REG_MR;
	send->s_wr.wr.fast_reg.length = len;
	send->s_wr.wr.fast_reg.rkey = send->s_mr->rkey;
	send->s_wr.wr.fast_reg.page_list = send->s_page_list;
	send->s_wr.wr.fast_reg.page_list_len = nent;
	send->s_wr.wr.fast_reg.page_shift = PAGE_SHIFT;
	send->s_wr.wr.fast_reg.access_flags = IB_ACCESS_REMOTE_WRITE;
	send->s_wr.wr.fast_reg.iova_start = sg_addr;

	ib_update_fast_reg_key(send->s_mr, send->s_remap_count++);
}

int rds_iw_xmit_rdma(struct rds_connection *conn, struct rm_rdma_op *op)
{
	struct rds_iw_connection *ic = conn->c_transport_data;
	struct rds_iw_send_work *send = NULL;
	struct rds_iw_send_work *first;
	struct rds_iw_send_work *prev;
	struct ib_send_wr *failed_wr;
	struct rds_iw_device *rds_iwdev;
	struct scatterlist *scat;
	unsigned long len;
	u64 remote_addr = op->op_remote_addr;
	u32 pos, fr_pos;
	u32 work_alloc;
	u32 i;
	u32 j;
	int sent;
	int ret;
	int num_sge;

	rds_iwdev = ib_get_client_data(ic->i_cm_id->device, &rds_iw_client);

	/* map the message the first time we see it */
	if (!op->op_mapped) {
		op->op_count = ib_dma_map_sg(ic->i_cm_id->device,
					     op->op_sg, op->op_nents, (op->op_write) ?
					     DMA_TO_DEVICE : DMA_FROM_DEVICE);
		rdsdebug("ic %p mapping op %p: %d\n", ic, op, op->op_count);
		if (op->op_count == 0) {
			rds_iw_stats_inc(s_iw_tx_sg_mapping_failure);
			ret = -ENOMEM; /* XXX ? */
			goto out;
		}

		op->op_mapped = 1;
	}

	if (!op->op_write) {
		/* Alloc space on the send queue for the fastreg */
		work_alloc = rds_iw_ring_alloc(&ic->i_send_ring, 1, &fr_pos);
		if (work_alloc != 1) {
			rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc);
			rds_iw_stats_inc(s_iw_tx_ring_full);
			ret = -ENOMEM;
			goto out;
		}
	}

	/*
	 * Instead of knowing how to return a partial rdma read/write we insist that there
	 * be enough work requests to send the entire message.
	 */
	i = ceil(op->op_count, rds_iwdev->max_sge);

	work_alloc = rds_iw_ring_alloc(&ic->i_send_ring, i, &pos);
	if (work_alloc != i) {
		rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc);
		rds_iw_stats_inc(s_iw_tx_ring_full);
		ret = -ENOMEM;
		goto out;
	}

	send = &ic->i_sends[pos];
	if (!op->op_write) {
		first = prev = &ic->i_sends[fr_pos];
	} else {
		first = send;
		prev = NULL;
	}
	scat = &op->op_sg[0];
	sent = 0;
	num_sge = op->op_count;

	for (i = 0; i < work_alloc && scat != &op->op_sg[op->op_count]; i++) {
		send->s_wr.send_flags = 0;
		send->s_queued = jiffies;

		/*
		 * We want to delay signaling completions just enough to get
		 * the batching benefits but not so much that we create dead time on the wire.
		 */
		if (ic->i_unsignaled_wrs-- == 0) {
			ic->i_unsignaled_wrs = rds_iw_sysctl_max_unsig_wrs;
			send->s_wr.send_flags = IB_SEND_SIGNALED;
		}

		/* To avoid the need to have the plumbing to invalidate the fastreg_mr used
		 * for local access after RDS is finished with it, using
		 * IB_WR_RDMA_READ_WITH_INV will invalidate it after the read has completed.
		 */
		if (op->op_write)
			send->s_wr.opcode = IB_WR_RDMA_WRITE;
		else
			send->s_wr.opcode = IB_WR_RDMA_READ_WITH_INV;

		send->s_wr.wr.rdma.remote_addr = remote_addr;
		send->s_wr.wr.rdma.rkey = op->op_rkey;
		send->s_op = op;

		if (num_sge > rds_iwdev->max_sge) {
			send->s_wr.num_sge = rds_iwdev->max_sge;
			num_sge -= rds_iwdev->max_sge;
		} else
			send->s_wr.num_sge = num_sge;

		send->s_wr.next = NULL;

		if (prev)
			prev->s_wr.next = &send->s_wr;

		for (j = 0; j < send->s_wr.num_sge && scat != &op->op_sg[op->op_count]; j++) {
			len = ib_sg_dma_len(ic->i_cm_id->device, scat);

			if (send->s_wr.opcode == IB_WR_RDMA_READ_WITH_INV)
				send->s_page_list->page_list[j] = ib_sg_dma_address(ic->i_cm_id->device, scat);
			else {
				send->s_sge[j].addr = ib_sg_dma_address(ic->i_cm_id->device, scat);
				send->s_sge[j].length = len;
				send->s_sge[j].lkey = rds_iw_local_dma_lkey(ic);
			}

			sent += len;
			rdsdebug("ic %p sent %d remote_addr %llu\n", ic, sent, remote_addr);
			remote_addr += len;

			scat++;
		}

		if (send->s_wr.opcode == IB_WR_RDMA_READ_WITH_INV) {
			send->s_wr.num_sge = 1;
			send->s_sge[0].addr = conn->c_xmit_rm->m_rs->rs_user_addr;
			send->s_sge[0].length = conn->c_xmit_rm->m_rs->rs_user_bytes;
			send->s_sge[0].lkey = ic->i_sends[fr_pos].s_mr->lkey;
		}

		rdsdebug("send %p wr %p num_sge %u next %p\n", send,
			&send->s_wr, send->s_wr.num_sge, send->s_wr.next);

		prev = send;
		if (++send == &ic->i_sends[ic->i_send_ring.w_nr])
			send = ic->i_sends;
	}

	/* if we finished the message then send completion owns it */
	if (scat == &op->op_sg[op->op_count])
		first->s_wr.send_flags = IB_SEND_SIGNALED;

	if (i < work_alloc) {
		rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc - i);
		work_alloc = i;
	}

	/* On iWARP, local memory access by a remote system (ie, RDMA Read) is not
	 * recommended.  Putting the lkey on the wire is a security hole, as it can
	 * allow for memory access to all of memory on the remote system.  Some
	 * adapters do not allow using the lkey for this at all.  To bypass this use a
	 * fastreg_mr (or possibly a dma_mr)
	 */
	if (!op->op_write) {
		rds_iw_build_send_fastreg(rds_iwdev, ic, &ic->i_sends[fr_pos],
			op->op_count, sent, conn->c_xmit_rm->m_rs->rs_user_addr);
		work_alloc++;
	}

	failed_wr = &first->s_wr;
	ret = ib_post_send(ic->i_cm_id->qp, &first->s_wr, &failed_wr);
	rdsdebug("ic %p first %p (wr %p) ret %d wr %p\n", ic,
		 first, &first->s_wr, ret, failed_wr);
	BUG_ON(failed_wr != &first->s_wr);
	if (ret) {
		printk(KERN_WARNING "RDS/IW: rdma ib_post_send to %pI4 "
		       "returned %d\n", &conn->c_faddr, ret);
		rds_iw_ring_unalloc(&ic->i_send_ring, work_alloc);
		goto out;
	}

out:
	return ret;
}

void rds_iw_xmit_complete(struct rds_connection *conn)
{
	struct rds_iw_connection *ic = conn->c_transport_data;

	/* We may have a pending ACK or window update we were unable
	 * to send previously (due to flow control). Try again. */
	rds_iw_attempt_ack(ic);
}